1. Field of the Invention
The present invention relates to the field of vehicular transport, specifically to the reduction of aerodynamic friction associated with such vehicles during operation.
2. Description of Related Technology
Most all vehicles which operate at an appreciable air velocity are subject to the effects of aerodynamic drag. Drag is undesirable in that it necessitates a greater energy output to maintain a given vehicle velocity as compared to the same situation without drag. This greater required energy output translates into reduced fuel efficiency (or energy efficiency for non-fossil fuel vehicles). Additionally, in the case of fossil fuel-powered vehicles, the expenditure of this additional energy necessarily results in increased combustion by-product emissions (including typically hydrocarbons and carbon monoxide) which may have any number of deleterious effects.
Aerodynamic drag results from the relative motion of the surrounding fluid (air) around the vehicle during operation. In the most simplistic case, the air is stagnant with respect to the ground such that the air and ground speeds of the vehicle are equivalent. However, a more accurate model recognizes that the air in any given location moves in relation to the ground in a complex manner. In general, however, the predominant source of aerodynamic drag in a ground vehicle on average is directly attributable to the vehicular motion in relation to the ground. That is, comparatively little aerodynamic drag is the result of factors such as headwinds, downdrafts, or the like. Hence, in a general sense, drag is proportional to the speed of the vehicle. Accordingly, at higher speeds, reduction of the aerodynamic drag associated with the forward motion of the vehicle through the air would in most cases produce a significant benefit in terms of increased efficiency.
A variety of different systems and techniques (both active and passive) have been employed on ground vehicles in an attempt to reduce aerodynamic drag. These systems and techniques have included the use of air dams and/or spoilers, conformal moldings and body components, variation in the angle and/or position of the cooling radiator, use of low-friction coatings, and the creation of low pressure areas in various portions of the vehicle to redirect air flow. While great strides have been made in reducing the aerodynamic drag associated with the typical passenger vehicle or tractor-trailer, further reductions in drag are still possible.
When evaluating the efficacy of any proposed system for reducing drag, consideration must be given to the overall energy balance of the vehicle. Specifically, a system which reduces aerodynamic drag at the expense of other efficiencies may not be desirable. In short, there must be a net savings in energy output for the vehicle under the prescribed operating conditions in order to warrant the use of the system. One solution to this problem is to utilize existing inefficiencies or losses to support operation of the drag reduction system. Hence, if existing systems and components can be used to accomplish these aims, further inefficiencies (such as those resulting from added weight and/or required power) can be reduced or even eliminated.
Another consideration relates to the changing operational environment of the typical ground vehicle. Such vehicles as a whole operate in relative extremes of temperature, humidity and precipitation, altitude, and particulate contamination (dust). Variations in humidity/precipitation, altitude, and temperature can affect aerodynamic drag and air density, thereby dictating that any viable drag reduction system be adaptive to such variations, or at a minimum effective in those environments in which the vehicle is predominantly operated.